Circuit breakers can interrupt a transfer of electric energy within a few milliseconds in electric switching devices. A drive of a circuit breaker of this type should therefore transfer the energy to the circuit breaker within the few milliseconds in which the switching process is to be performed.
Known circuit breakers are only switched a few times during an operating year, such as if a short circuit occurs. In addition, the circuit breaker is installed for many decades. In this respect, a drive of a circuit breaker should demonstrate not just a high level of instantaneous reliability but also need little maintenance.
Based on this background, DE 10 2009 015 881 A1 discloses a hydromechanical drive having a working cylinder that actuates a circuit breaker through a piston rod. This drive includes an energy storage device and a hydraulic device for transmitting energy that is stored in the energy storage device.
The known hydromechanical drive stores the energy for the switching process in metal springs of a resilient energy storage device, wherein the hydraulic device ensures that energy is transmitted in a low loss and low wear manner during the switching process.
However, the hitherto known hydraulic devices includes working cylinders that are constructed in a relatively complex manner. The known drives include single part working cylinders with a complex structure and said cylinders call for diverse components such as a tank housing, supporting pipes and damping rings. The production process for these complex working cylinders is extremely complex and is accompanied by high costs.
For example, the running surfaces for a piston rod of the working cylinder can be anodized. This is encumbered with a high outlay and consequently high costs. In the case of using aluminum, cavitation damage can occur that can cause technical problems.